1. Field of the Invention
The present invention relates to a method for forming a coating film of a coating liquid on the peripheral surface of a cylinder/column-shaped substrate for use in charging, development, transfer, fixing, pressurizing or the like in an electrophotographic apparatus such as a copier or a printer, and a method for producing an electrophotographic fixing member.
2. Description of the Related Art
In an electrophotographic apparatus such as a copier or a printer, a member such as a cylinder/column-shaped belt or roller is used in various processes such as charging, development, transfer, fixing and pressurizing. In such a member, a functional film for exhibiting a required function is formed on a substrate depending on the application of the member. In the present specification, a cylinder-shaped substrate or a column-shaped substrate is also simply referred to as “substrate” in some cases.
Such a functional film can be formed by forming a coating film of a coating material for forming the functional film on the peripheral surface of the substrate, and drying or if necessary curing the coating film. Then, as a method for forming the coating film on the peripheral surface of the substrate, a spiral method is known (see Japanese Patent Application Laid-Open No. 2002-370065).
The spiral method is a method in which, while allowing a substrate to relatively rotate against a coating liquid-supplying unit and also allowing the coating liquid-supplying unit and the substrate to relatively move in the direction along with the rotation axis of the substrate, a coating liquid is supplied from the coating liquid-supplying unit to form a coating film on the peripheral surface of the substrate.
The spiral method can shorten the time required for coating with the coating material, and achieve the high use efficiency of the coating liquid. Therefore, a reduction in production cost can be achieved.
According to studies by the present inventors, however, the coating film formed by using the spiral method may have spiral unevenness in thickness due to the rotation period of the substrate.
The functional film of the member for use in the electrophotographic apparatus, if having an uneven thickness, may have an influence on the quality of an electrophotographic image. Therefore, the coating film formed on the substrate is required to be highly uniform in thickness.
In particular, a fixing member having a layer formed by curing an addition curing type silicone rubber composition (hereinafter, also referred to as “cured silicone rubber layer”) is often used in a thermal fixing apparatus of the electrophotographic apparatus. In such a fixing member, a primer layer is formed on the peripheral surface of the substrate before formation of the cured silicone rubber layer, in order to allow the substrate and the cured silicone rubber layer to tightly adhere to each other.
Here, the primer layer may include a reactive component with an unsaturated aliphatic group (vinyl group) included in the cured silicone rubber layer to be formed thereon. In such a case, the reactive component may be transferred from the primer layer to the cured silicone rubber layer, and the reactive component and the unsaturated aliphatic group may react with each other in the cured silicone rubber layer, resulting in an increase in hardness of the cured silicone rubber layer. If the primer layer here has partial unevenness in thickness, the amount of the reactive component transferred to the cured silicone rubber layer is partially different, resulting in causing partial unevenness in hardness of the cured silicone rubber layer. Such partial unevenness in hardness of the cured silicone rubber layer can cause unevenness in melting of a toner in thermal fixing of an electrophotographic image, thereby causing unevenness in gloss in the electrophotographic image.
Therefore, the present inventors have recognized that if a coating film of a raw material for primer layer formation is formed on the substrate by using the spiral method that is advantageous in terms of costs, a new technique is required to be developed in order to cause no spiral unevenness in thickness on the coating film.
Then, the present invention is directed to providing a method for forming a coating film, which can more suppress the occurrence of unevenness in thickness of a coating film in formation of the coating film on the peripheral surface of a substrate.
Further, the present invention is directed to providing a method for producing an electrophotographic fixing member, which contributes to formation of a high-quality electrophotographic image.